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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science, Ltd
    Journal of neuroendocrinology 14 (2002), S. 0 
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The preoptic area is an important brain region controlling sex-typic behaviour and physiology, and astrocytes of this region are responsive to steroids perinatally. Utilizing glial fibrillary acidic protein immunocytochemistry, the morphology of astrocytes in the preoptic area of male and female rat pups was examined on the day of birth and on postnatal day 3. As early as the day of birth, astrocytes of the male preoptic area exhibit both significantly greater primary process length and number of primary processes, and these differences remain at postnatal day 3. Application of exogenous steroid to females suggested that gonadal steroids, in particular oestradiol, mediate the sex difference. Pups received 100 µg of steroid on the day of birth and again on postnatal day 1, and astrocyte morphology was assessed on postnatal day 3. Both oestradiol and testosterone induced significant changes in process length and number compared to vehicle-treated controls. Astrocytes of oestradiol-treated females did not differ on PN3 from those of PN3-untreated males. Exposure to the nonaromatizable steroid, dihydrotestosterone, had no effect on any attribute of astrocyte morphology. This suggests the effects induced by testosterone are mediated by oestradiol following local aromatization of the steroid, and not through direct activation of the androgen receptor. Astrocytes are important in synapse formation and efficacy, and we hypothesize a role for astrocyte complexity and differentiation in the establishment of synaptic patterning.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science, Ltd
    Journal of neuroendocrinology 14 (2002), S. 0 
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Our previous work has demonstrated that astrocytes in the developing arcuate nucleus of the rat hypothalamus are sexually dimorphic as a result of differential exposure to oestradiol. Moreover, our experiments in neonatal rats suggest an absence of oestrogen receptors (ER) in arcuate nucleus astrocytes in vivo. This, along with the conspicuous lack of evidence in the literature confirming the presence of ER in arcuate nucleus astrocytes of the neonatal rat brain, led us to question the mechanism by which oestrogen induces changes in arcuate nucleus astrocyte morphology. Based on our previous findings that oestradiol increases γ-aminobutyric acid (GABA) levels in the neonatal rat arcuate, we hypothesize that GABA is released from neighbouring oestrogen-sensitive neurones and alters arcuate nucleus astrocyte morphology. Here, we report that in vivo reduction of GABA synthesis in the neonatal rat brain by antisense oligodeoxynucleotides to glutamic acid decarboxylase prevented gonadal steroid-induced astrocyte differentiation in males and testosterone-treated females. Conversely, activation of GABAA receptors with the agonist muscimol increased astrocyte differentiation in females in the absence of gonadal steroids. Given that GABA is made only in neurones and that its synthesis is increased by oestradiol, we conclude that it acts as a diffusible factor inducing the differentiation of neighbouring astrocytes.
    Type of Medium: Electronic Resource
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